The present invention relates to a spectacle lens image sensing processing apparatus and spectacle lens positioning method which can be suitably used for a layout blocker for determining a lens processing center or the like for edging of a spectacle lens and mounting a processing jig at the processing center.
In general, when a lens blank (uncut lens) is to be edged into a shape conforming to the frame of an eyeglass frame, the optical characteristics of the prescription lens, e.g., the optical center, geometrical center, diameter, eyepoint position, lens power, and cylinder axis are checked in the pre-process, and a processing center, the mounting angle of a processing jig (to be generally called a lens holder) with respect to the lens, and the like (optical layout) are determined from the lens information, lens frame shape data, and prescription data about a wearer. On the basis of this information, the center of the lens holder is positioned to the processing center of the lens, and the lens holder is mounted on the lens surface (blocking). In general, the processing center of the lens coincides with the eyepoint position of the lens. In processing, the rim of the lens is edged by a grind stone or cutter to match the pupil center (eyepoint) of a wearer to the eyepoint position of the lens, thereby processing the lens into a shape conforming to the shape of an eyeglass frame.
Conventionally, an optical layout procedure and blocking for a lens, which are included in the pre-process for edging of the lens, are manually performed by an operator using specialized devices. For example, the lens power of a lens to be examined is measured by a power measuring device called a lens meter.
When a lens 1 to be examined is a progressive multifocal lens, micro engraved marks 3A and 3B are formed at reference positions spaced apart from a geometrical center O by a predetermined distance, as shown in FIG. 17. Since the lens 1 is designed to derive the geometrical center O, the optical centers of distance and near portions, an eyepoint 11, and the like from the positions of these micro engraved marks 3A and 3B, the position of the eyepoint 11 is detected from the positions of these micro engraved marks 3A and 3B, and a lens holder is mounted at the position of the eyepoint 11. FIG. 18 shows another example of the progressive multifocal lens 1. The progressive multifocal lens 1 shown in FIG. 18 is a right-eye lens whose micro engraved marks 3A and 3B both are circular.
In an optician""s shop, when the position of the eyepoint 11 is to be detected from the micro engraved marks 3A and 3B, the marks are generally detected by a visual check or optically. In the case of a visual check, the micro engraved marks 3A and 3B are detected by holding the lens to light from a light source such as a fluorescent lamp, and the detected position is marked with a marker. Thereafter, the position of the eyepoint 11 is determined by using a sheet called a remark chart for a progressive multifocal lens. The remark chart lists actual-size images of progressive multifocal lenses by lens type, showing the positions of micro engraved marks, geometrical centers, distance power measuring portions, near power measuring portions, the positions of eyepoints, and the like. The lens 1 on which the positions of the micro engraved marks 3A and 3B are marked is placed on this chart. In this case, the lens 1 is placed on an image of the same type of lens as the lens to be examined of the lenses listed on the remark chart, and the positions of the micro engraved marks 3A and 3B marked on the lens 1 are matched to the positions of the micro engraved marks shown on the remark chart. The position of the eyepoint shown on the remark chart is indicated on the convex surface of the lens 1 with a marker. Thereafter, the center of the lens holder is positioned to the marked eyepoint 11, and the lens holder is mounted.
As a method of positioning a lens and lens holder by optically detecting the micro engraved marks 3A and 3B, for example, the spectacle lens positioning method and apparatus disclosed in Japanese Patent Laid-Open No. 11-295672 (to be referred to as the prior art hereinafter) are known. According to this prior art, a spectacle lens is positioned on the basis of the positional relationship and positional information of positioning marks (micro engraved marks, addition power) formed on the convex surface of the spectacle lens. An illumination adjustment lens is interposed between an illumination unit and the spectacle lens to irradiate the spectacle lens with light emitted from the illumination unit from the concave surface side through the illumination adjustment lens, and an image on the concave surface is sensed by an image input means such as a CCD. This sensed image is processed by an image processing unit to detect the positioning marks. A computation is then made to establish a predetermined positional relationship between the horizontal reference line of the spectacle lens and the position of an optical center on the basis of the positional relationship and positional information of these marks. The spectacle lens is positioned on the basis of the computation result.
If the lens to be examined is a multifocal lens (in general, a bi-focal lens), no micro engraved marks are formed on the lens unlike the progressive multifocal lens 1 described above. In general, therefore, as shown in FIG. 19, this lens is designed to obtain the positions of an geometrical center O and eyepoint 16 with reference to an upper rim 17 of a segment 13B. Therefore, when the position of the eyepoint 16 is to be detected by a visual check, the position of the eyepoint 16 can be determined by using a remark chart for multifocal lenses as in the case of the progressive multifocal lens 1 described above. When this position is to be optically detected, the lens positioning method and apparatus disclosed in the prior art can be used.
As described above, in the prior art, an optical layout procedure and blocking for a lens, which are included in the pre-process for edging of the lens, are manually performed by an operator using specialized devices. This processing is very inefficient and low in productivity, and hence becomes a serious hindrance to labor savings. In addition, since an operator must handle the lens with great care so as not to soil, damage, and break it, a significant burden is imposed on the operator. For this reason, demands have recently arisen for the development of an ABS (Auto Blocker for Single vision lens) for single-focus lenses and ABM (Auto Blocker for Multifocus lens) for progressive multifocal lenses and multifocal lenses, which are designed to automatically perform an optical layout procedure for a lens and lens blocking with a lens holder, thereby improving operation efficiency. In designing an ABM, in particular, since two types of lenses, i.e., a progressive multifocal lens and multifocal lens, are handled, the apparatus is required to have a device for sensing an image of the convex surface of a lens, detecting micro engraved marks or the upper rim of a segment by performing image processing for the sensed image, and detecting the optical characteristics (the position of a geometrical center, the position of an eyepoint, and the like) of the lens from these pieces of positional information as well as a lens meter for measuring a lens power.
Lens meters have been known, and, for example, the lens meters disclosed in Japanese Patent Laid-Open Nos. 49-122355 and 60-17355 and Japanese Patent Publication No. 8-20334 can be used. As a device for detecting the optical characteristics of a lens, the positioning method and apparatus disclosed in the above reference can be used. However, these positioning method and apparatus are difficult to apply to a lens having an astigmatic power, and hence are not practical. That is, in the prior art, since the light source and image sensing means are respectively arranged on the convex surface side and concave surface side of a lens, if the lens has an astigmatic power, the image sensed by the image sensing means distorts due to the cylinder axis, and image processing demands complicated correction, regardless of whether the lens is a single-focus lens, multifocal lens, or progressive multifocal lens.
As a technique of accurately and automatically positioning the progressive multifocal lens 1 and lens holder by detecting the micro engraved marks 3A and 3B, a method of image-sensing the progressive multifocal lens 1 upon optically magnifying it, detecting the positions of the micro engraved marks 3A and 3B from the sensed input image by template matching of comparing the input image with a prepared partial image (template), and calculating the position of the eyepoint 11 from the detected positions is known.
The progressive multifocal lens 1 is image-sensed after it is optically magnified for the following reason. If the lens is image-sensed without optically magnifying it, the resultant image becomes as small as several pixels. In using template matching, however, an image having a size of at least 10xc3x9710 pixels is required. According to this method using template matching, the progressive multifocal lens 1 and lens holder can be accurately positioned.
In the method using template matching, however, since the progressive multifocal lens 1 must be image-sensed after it is optically magnified, a magnifying optical system is required, resulting in an increase in cost. In addition, template matching requires much time.
As another method of detecting the position of an eyepoint 16 of a multifocal lens 13 from the contour shape of a segment 13B, the spectacle lens positioning apparatus disclosed in Japanese Patent Laid-Open No. 6-79600 is known. This positioning apparatus is designed to image-sense the multifocal lens 13 to be processed by using a video camera and display the sensed contour image of the segment 13B of the multifocal lens 13 on the screen of a TV monitor. The apparatus is also designed to calculate the contour image data of the segment 13B from the processing information about the multifocal lens 13 which is stored in advance and display the calculated contour image as a reference image on the screen of the TV monitor.
An operator moves a slide table, on which the multifocal lens 13 is mounted, to superimpose on the reference image the real image of the contour line of the segment 13B displayed on the screen of the TV monitor, thereby positioning the multifocal lens 13 to the normal position. After this positioning, a pad printer of a marking unit transfers a cross-shaped mark corresponding to a processing reference line onto a predetermined position on the multifocal lens 13. As described above, the positioning apparatus disclosed in Japanese Patent Laid-Open No. 6-79600 is designed to position the multifocal lens 13 while watching the TV monitor instead of a remark chart.
Although the positioning apparatus disclosed in Japanese Patent Laid-Open No. 6-79600 saves an operator from marking the multifocal lens 13, the operator must manually position the multifocal lens 13 while watching the screen of the TV monitor. This imposes a great burden on the operator as in the case of a remark chart.
It is an object of the present invention to provide a spectacle lens image sensing processing apparatus which can easily perform image processing for even a lens having an astigmatic power and detect optical characteristics of the lens, and more specifically a geometrical center and eyepoint position. It is another object of the present invention to provide a spectacle lens image sensing processing apparatus which can also measure a lens power.
It is still another object of the present invention to provide a spectacle lens positioning method and spectacle lens image sensing processing apparatus which can accurately position a progressive multifocal lens and a lens holder at a lower cost more efficiently and quickly than the prior art.
It is still another object of the present invention to provide a spectacle lens positioning method and spectacle lens image sensing processing apparatus which can accurately position a multifocal lens and a lens holder more efficiently and quickly than the prior art.
In order to achieve the above objects, according to the present invention, there is provided a spectacle lens image sensing processing apparatus for irradiating a convex surface of a lens to be examined with light from a light source, projecting an image of the convex surface onto image display means placed on a concave surface side of the lens, sensing the image of the convex surface, projected on the image display means, by using an image sensing unit, and performing image processing for the image of the convex surface sensed by the image sensing unit by using an image processing unit, thereby detecting an optical characteristic of the lens, wherein the image sensing unit is placed together with the light source on the convex surface side of the lens, the image display means is formed by a reflection screen, and the image of the convex surface of the lens is reflected by the reflection screen to return to the convex surface side of the lens, thereby forming the image on the image sensing unit.